Doubt over tests for hearing loss from congenital cytomegalovirus

Hearing loss at birth associated with congenital cytomegalovirus (cCMV) infection cannot be reliably predicted by the amount of virus in saliva or blood spots, US research suggests.

The condition, which can lead to other complications in the future such as further hearing impairment and physical or mental disabilities, is hard to identify as only one in 10 babies born with it display symptoms straight away.

Dr Shannon Ross and Dr Suresh Boppana, both from the University of Alabama, led the investigation as part of the NIDCD CHIMES study.

cCMV is the most common congenital infection, occurring in around 0.5% to 1% of all newly born babies.

Viral loads can be measured in both dried blood spots and also saliva, so the researchers set out to determine just how useful both were in identifying infants with symptomatic cCMV and CMV-associated sensorineural hearing loss (SNHL) at birth.

They assessed a total of 100,332 newborns at seven hospitals in the US. The babies were screened for CMV by testing saliva and dried blood spots using rapid culture and/or real-time polymerase chain reaction testing.

Some 462 had confirmed cCMV. Of these, 52 had symptomatic infection at birth and 35 had hearing loss at birth.

Among those with hearing loss, 15 also had symptomatic infection and 20 were asymptomatic.

Dried blood spots, on the other hand, were not significantly statistically different between symptomatic and asymptomatic infants.

Symptomatic infants had higher median saliva viral load than asymptomatic infants, while median viral loads in dried blood spots and saliva were not different for those with SNHL at birth and those with normal hearing.

Dr Ross said: “Until a reliable clinical or laboratory marker for hearing loss is identified, all infants with congenital CMV infection need regular hearing testing to monitor for the development of hearing loss.”

Introduction/Objectives: Congenital cytomegalovirus infection (cCMV) is an important cause of sensorineural hearing loss (SNHL). We sought to determine if DBS (dried blood spot) and saliva viral load at birth are useful in identifying infants with symptomatic cCMV and CMV-associated SNHL at birth.

Methods: Newborns at 7 U.S. hospitals were screened for CMV by testing saliva by rapid culture and/or real-time PCR. DBS were tested by real-time PCR. Infants with generalized petechial rash, purpura, hepatosplenomegaly, jaundice with direct hyperbilirubinemia, chorioretinitis or CNS involvement (microcephaly, seizures and focal deficits) were considered symptomatic. DBS and saliva viral loads were compared between symptomatic and asymptomatic infants and those with and without SNHL at birth.

Results: 462 of 100,605 infants screened had confirmed cCMV. Viral load in DBS did not differ between symptomatic and asymptomatic infants (2.2x103 vs 2.5x103 IU/ml, p=0.26). Symptomatic infants had higher median saliva viral load (7.0 x106 IU/mL, range: 1.2x102–5.5 x109) than asymptomatic infants (1.8 x106 IU/mL, range: 3.5x102–1.8 x1010; p=0.001). Median viral loads in the DBS and saliva were not different for those with SNHL at birth and those with normal hearing.

Conclusions: Saliva CMV viral loads are higher in symptomatic infants compared with asymptomatic babies; however, these measurements are of limited value because of the overlap between the groups. DBS viral loads do not differ between asymptomatic and symptomatic infants. The wide variability in viral loads and the overlap between groups suggests that virus burden in DBS and saliva cannot reliably identify infants with newborn disease and SNHL at birth.

From students to nurses, we provide our subscribers with the information and tools they need to be successful, well informed, up to date with the latest practice - and most importantly - to be the best nurses they can be.

Nursing Times Jobs

Whether you are just starting out in your nursing career or you are an experienced nursing professional, we aim to make your job searching simple and effective.

We provide you with nursing jobs from all sectors, so why not start your
search today?